In the prior art fuse, a small bulb is connected between two metal electrodes. The bulb has a larger resistor which is greater than that of the fuse so that current only flows through the fuse instead of the bulb. Thus the bulb will not light up. When the fuse breaks due to overload, the current flows through the bulb so that the bulb will lightup. However the prior art bulb easily burns so that the current with over-current can no be formed easily. Thus the repair work needs a long time. Thereby the bulb in the prior art is protruded from the conventional fuse structure so that it is not suitable to be installed within a car.
“Blade fuses” have now substantially replaced the tubular glass fuses that were once standard in the automotive industry. A disadvantageous feature of such blade fuses is however that, when installed in a fuse block, the fusible element or link is hidden from view. Locating a blown fuse therefore normally entails withdrawal of the fuses from the block, one-by-one until the defective fuse is found.
In one prior art, U.S. Pat. No. 5,598,138, a fault-indicating blade fuse is disclosed. The fuse comprises a relatively thin and flat, generally rectangular, dielectric body defined by top, bottom and opposite side margins, and having an upper portion of long, narrow profile, taken in transverse cross section; a pair of generally parallel metal blades projecting downwardly beyond the bottom margin of the body; a link within the body electrically interconnecting the blades and being fusible to break the interconnection when subjected to current exceeding a rated value; and a light-emitting electrical device positioned for ready visibility from above the fuse and lying within the bounds of the upper body profile, the light-emitting device being so constructed and so connected to the blades as to be activated, for light emission, upon fusion of the link when subjected to such excessive current. The light-emitting device is selected from the group consisting of incandescent lamps and at least one light-emitting diode. Furthermore, the light-emitting device comprises first and second light-emitting diodes connected in parallel and biased for passage of direct current between the blades in opposite directions, the diodes thereby affording dual polarity to the fault-indicating feature of the fuse.
However this prior art is a unidirectionally device. In installation, the fuse must be placed in a predetermined orientation. This induces a trouble in the installation. Furthermore, the LED is not firmly secured to the fuse. The fuse wire is welded to the fuse plate so that the connection of the prior art is not tight. However all these are necessary to be improved.